Laboratory Study On Oilfield Produced Water For Preparing Polymer Solution

Polymer flooding of EOR is widely used in oilfield at domestic and abroad. At present, the preparation injection technology used in Shengli Oilfield is polymer solution prepared with fresh water and then diluted by oil produced water. Oil produced water dilution has a bad influence on the viscosity of polymer solution and flooding effect because of the higher salinity and unqualified water. So, that oil produced water treated by water quality modification replaces fresh water to prepare polymer solution has a great realistic economical significance and far-reaching social benefits on raising viscosity, saving fresh water, reducing waste water, enhancing environmental protection and increasing the effects and benefits of polymer flooding. In this paper, the water-related factors such as the types and contents of metal ions, dissolved oxygen, suspended particles,bacterium which influence the viscosity and degree of polymer solution are systematically studied and the water quality-controlling targets and the limits are put forward. The synthetical water-quality-modification treatment agent SC which can increase the initial viscosity and stabilize the higher initial viscosity is developed and its performance is evaluated comprehensively. The results show that SC has a good viscosity-increasing ability, rheological property and corrosion inhibitive effect to some extent. The technical economic feasibility and applicability of the technology that oil produced water treated by water quality modification prepares polymer solution are explored and the mechanism of action of SC is analyzed. Intermediate productive test of SC is conducted and the process flow of preparing polymer solution by oil produced water is designed. Field application test in Gudong oil production plant of Shengli Oilfield is carried out. Field monitor data indicates that when the dosage of SC is 600 mg.L-1, the initial and after-40-days viscosity of polymer solution prepared by oil produed water from Dong 3 CPU of Gudong oilfield treated by water quality modification are equal to the viscosity of polymer solution prepared with fresh water and diluted by oil produced water and the majority of high valence metal ions are removed. The feasibility that oil produced water treated by water quality modification replaces fresh water to prepare polymer solution is verified and achieved.